In recent years, small-scale light electronic devices with multi-functionality and high functionality are becoming widespread and a greater level of integration of installed electronic components is being demanded. In response to such demands, the number of each type of electronic component being manufactured as a semiconductor device is increasing. In addition, a wide variety of sensors are being manufactured as small-scale semiconductor devices apart from semiconductor devices manufactured as circuit components. For example, a dynamic quantity sensor having a small-scale simple structure is realized using MEMS (Micro Electro Mechanical Systems) technology. As a dynamic quantity sensor (known as a piezo resistor type sensor) for example, a moving part which displaces according an external force is formed using a semiconductor substrate and a dynamic quantity sensor which detects the displacement of this moving part using a piezo resistor element is realized in an acceleration sensor or angular velocity sensor.
In the dynamic quantity sensor described above, various packages are used in order to stabilize and displace a movable part of the sensor. For example, the semiconductor substrate formed with a sensor is covered with a cap component and a resin package for sealing the cap component is used with a resin mold etc. In addition, a ceramic package is used to house and seal the semiconductor substrate formed with the sensor.
However, there was a problem in the case where a resin package is used whereby a sensor receives stress in the packaging process due to a difference in a linear expansion coefficient between a semiconductor substrate formed with the sensor and a resin mold, and sensor characteristics such as an offset voltage or sensitivity etc vary after the sensor is packaged. After the sensor is packaged the stress received during the packaging process remains and the stress received by the sensor changes due to a change in temperature added within a sensor specifications range. Because the amount by which the resin expands is large compared the amount of expansion of the semiconductor substrate when the added temperature reaches a high level, the stress received by the sensor is relaxed. However, because the amount by which the resin contracts is large compared the amount of contraction of the semiconductor substrate when the added temperature is a low level, the stress received by the sensor increases. Furthermore, in case of ceramic packaging, because the difference in a linear expansion coefficient between a semiconductor substrate and a ceramic is small and the ceramic itself has a high level of rigidity, the amount of change in stress received by the sensor due to a change in temperature is small and the effects on the sensor's characteristics is slight. However, since the costs of ceramic packaging are high compared to resin packaging, the manufacturing costs of the dynamic quantity sensor increase.
For example, an acceleration sensor described in Japanese Laid Open Patent 2006-300904, Japanese Laid Open Patent 2005-337874, Japanese Laid Open Patent 2000-46862 and Japanese Laid Open Patent 2009-53180, and an inertial sensor described in Japanese Laid Open Patent H11-1337571 are proposed as a structure for relaxing the stress received by a sensor during the packaging process described above. A slit is formed to pass through the sensor including a cap component in the acceleration sensor in Japanese Laid Open Patent 2006-300904. In the acceleration sensor in Japanese Laid Open Patent 2005-337874, an internal frame formed with the sensor and an external frame which encloses the external periphery of the internal frame are joined together by a stress relaxation beam. In the acceleration sensor in Japanese Laid Open Patent 2000-46862, a curved part is arranged on a distorted part which swingably supports a spindle which becomes a movable part. In the sensor in Japanese Laid Open Patent 2009-53180, a stress buffer is arranged on at least one part of a beam. In addition, in the inertia sensor in Japanese Laid Open Patent H11-337571, a slit for reducing thermal stress is arranged on the external periphery edge of a diaphragm.
However, the acceleration sensors described in Japanese Laid Open Patent 2006-300904, Japanese Laid Open Patent 2005-337874, Japanese Laid Open Patent 2000-46862 and Japanese Laid Open Patent 2009-53180, and the inertial sensor described in Japanese Laid Open Patent H11-1337571 have the following problems.
In the acceleration sensor in Japanese Laid Open Patent 2006-300904, because a slit which passes through the sensor including a cap component is formed the sensor does not have a structure for relaxing stress. In addition, the acceleration sensor in Japanese Laid Open Patent 2006-300904 does not consider using resin packaging. That is, in the case where resin packaging is used in the acceleration sensor in Japanese Laid Open Patent 2006-300904, stress received by the sensor in the resin packaging process can't be reduced because resin enters the slit part. In the acceleration sensor in Japanese Laid Open Patent 2005-337874, although an internal frame formed with the sensor and an external frame which encloses the external periphery of the internal frame are joined together by a stress relaxation beam, because the length of the stress relaxation beam is longer than the length of one edge of the sensor, when the resonance frequency of the sensor due to an external force is considered, in order to realize a stress relaxation beam of a sufficiently higher resonance frequency than the resonance frequency of the sensor it is necessary to increase the width of the stress relaxation beam. Because the level of design freedom of a wiring layout is reduced when the width of the stress relaxation beam is increased, the area of the semiconductor substrate formed with the sensor and stress relaxation beam is increased, which acts counter to the demands for small scale. In any of the structures of the acceleration sensors in Japanese Laid Open Patent 2000-46862 and Japanese Laid Open Patent 2009-53180 and the inertia sensor in Japanese Laid Open Patent H11-33751 it is difficult to maintain the sensor's characteristics in the case where stress is received from resin packaging, in particular, it is difficult to reduce changes in temperature characteristics along a Z axis in the case where stress from resin packaging is received.
The present invention attempts to solve the problems described above and aims to provide a dynamic quantity sensor which reduces stress received by the sensor due to resin packaging and controls variation in sensor characteristics due to stress.